1. Field of the Invention
This invention generally relates to machinery for handling elongate materials, and more specifically to a continuously balanced apparatus for storing and dispensing elongate materials.
2. Description of the Prior Art
It is frequently required during manufacture to utilize machinery which must be supplied with elongate materials from pay off devices, such as reels or bobbins or, in some instances, in relatively flat packages sometimes referred to as "flat pancake" packages, in which a flat strip of material is wound as a single row consisting of a series of overlapping convolutions. However the capacity of such packages is limited. Additionally, such packages are available from a large number of suppliers. Therefore, in many instances, the packages are not compatible or immediately mountable on the machinery being used and, therefore, the packages must first be rewound or otherwise arranged to be usable with the machinery. Such rewinding normally involves down time of the machinery thereby resulting in a loss of output and operating efficiency.
Numerous attempts have been made to overcome the problems of feeding continuous elongate materials. For example, strip accumulators have been proposed which allows strip to be fed into the accumulator at a speed faster than the strip is removed for processing, thereby causing excess strip to be stored within the accumulator. In this manner, processing can continue by utilizing the stored strip while the lead end of a new coil is welded to the end of the last coil to be fed to the accumulator. However, such strip accumulators are typically stationary and, therefore, the use of the stored strip in conjunction with rotating machinery may present difficulties, including multiple twists or bends of the strip material as it is fed to the processing zone of the machine.
An attempt to supply rotating machinery with a supply of strip material is disclosed is U.S. Pat. No. 4,597,276, wherein a supply reel in the nature of a "pancake" package is mounted on a rotating head or support plate, the end of the strip being guided by rollers mounted on the rotating plate and fed to a central zone along the axis of the rotating machine where the strip is helically wound to manufacture interlocked tubular pipe. In the aforementioned patent, the strip material must first be wound on the reel, which is adapted to be mounted on the rotating support plate. The reels which are mounted on the rotating support plate are typically wound in a separate operation prior to mounting on the support plate. Once mounted on the rotating plate, the machinery can operate continuously until the reel is empty, at which time the machine must be stopped, the reel rewound in a separate operation or the reel must be replaced with another similar reel which has been prepared for this purpose. Additionally, in order to attach the end of a first strip to the beginning end of a new strip, the ends of the respective strips must be welded or otherwise attached to each other. A major disadvantage with the approach disclosed in this patent is that the reel is mounted eccentrically or spaced from the machine axis of rotation of the rotating plate, thereby presenting an unbalanced condition which can become intolerable unless compensated with appropriate counterweight measures. However, because the weight of the reel changes continuously as it is emptied and the strip is consumed, the extent of unbalance also changes continuously during the operation of the machine, which makes it more difficult to compensate for the weight of the reel and provide the proper balance during the entire unwinding operation. The patent does not disclose any counterbalance or counterweight measures, and to provide perfect compensation and rotational stability of the rotating head during the entire work cycle of the reel would be both complex and expensive. The off balance conditions represented by the patent design also limits the amount of strip material that can be mounted on the rotating plate, and irrespective of the number of reels that can be mounted on the machine, the almost certain imbalances which will result limit the usefulness of the design.
In British Patent No. 1,010,167, a machine is disclosed for the helical winding of tapes and the like. The apparatus disclosed in the patent is an attempt to provide a reservoir of strip-type material on a rotating machine which allows for the connection of the end of a first strip to the beginning of a new strip without interruption of the operation of the machine, so that the rotating machine may enjoy the same advantages as those involved with stationary strip accumulators. The machine disclosed in this patent includes a fixed support on which there is wound tape or strip material from a feed roller spool to form concentric revolutions or turns on a set of rollers carried by a rotatably mounted annular plate. The inner turns of the so formed helical arrangement are dispensed and wound onto a mandrel in the central region of the rotating annular plate. The rollers are so mounted on the annular plate as to be movable towards a fictitious center in order to permit the variation of the perimeter of a polygon which is defined by the points where the rollers are mounted and along which the different concentric convolutions of the tape are formed. The rollers are caused to move outwardly during normal operation to keep the tape under constant mechanical tension. When the feed roller spool is exhausted, the rollers are adapted to move inwardly, during continued rotation of the annular plate, to compensate for the fixing of the position of the free end of the tape while it is connected to the leading end of a fresh roll or spool. The intention of the apparatus disclosed in the British patent is to allow a fresh spool to be connected to the end of a strip which had been stored on the rotating plate without stopping the machine. However, the arrangement proposed in the British patent has a number of disadvantages. The change in diameter or dimensions of the polygon as a result of the inward movement of the rollers is relatively small compared to the average diameter defined by the rollers on the supporting annular plate. Therefore, when the end of the strip is gripped and fixed in position for the purpose of attachment to a new supply reel, the continued rotation of the annular plate causes a rapid change in the capacity or amount of wire stored on the rollers. The inward movement of the rollers only compensates for a part of that depletion and, since the stored or cumulative capacity to give up wire is a function of the change in the diameter of the stored loop as well as the number of turns, a large number of turns must normally be used to provide the requisite cumulative capacity required during the strip attachment cycle. However, as the number of turns is increased, the system is more prone to locking up or freezing once the ends are joined and a strip from a new supply is fed to the apparatus for restoring or replenishing the reservoir of wire on the rollers. Any effort to increase the diameter about which the rollers are mounted in order to increase the cumulative capacity, in an effort to reduce the number of turns, aggravates the condition because the amount of wire depleted during each turn of the annular plate increases once the end of the strip is fixed in position. Therefore, any attempt to increase the cumulative capacity by increasing the radius of the rollers or increasing the number of turns stored on the rollers would create difficulties and make the machine inoperative. As suggested, the problem with the machine disclosed in the British patent is that it attempts to provide a continuous helical winding of a tape or strip without ever stopping the machine, which necessitates the periodic gripping and fixing the position of a trailing strip end for the purpose of attachment to a next successive supply reel.
In the case of heavier or thicker strip materials, such as stainless steel strip, it has, in some cases, been required to transfer the strip from its payoff device with a number of twists from the plane of the strip. It is usually preferred that such twists be minimized or eliminated, as are bends of the strips about small diameter in order to minimize friction and damage to the strip. For example, in U.S. Pat. No. 4,783,980, issued to Ceeco Machinery Manufacturing Limited, the assignee of the instant application, an apparatus is disclosed for making helically wound interlocked flexible pipe. Two supply reels or dummy spools are provided one of which is active to supply strip material to produce the pipe while the other is loaded with strip material from external flat pancake reels to serve as a substantial reservoir of strip material which takes over when the active reel gives up all of its strip material. Since rewinding can be effected at a higher speed than the normal dispensing speed of the machine, the rewound bobbin can be filed from a number of flat pancakes, suitably joined before it is time to switch dummy spools. Rewinding of an empty dummy spool does not result in down time because the procedure does not interfere with the dispensing of the strip material from the other, active spool. However, in order to refill the dummy spools and dispense the strip material, it passes over a number of pullies or rollers and is twisted a number of times out of its plane. While this may be acceptable for most strip materials, the disclosed arrangement becomes impractical for larger dimensioned strip materials used to produce flexible pipe needed to withstand ever increasing pressures.